The present invention relates generally to magnetic resonance imaging (MRI), and more particularly to, a pulse sequence, method, and apparatus for multi-slice acquisition using fast spin echo imaging to acquire black blood contrast images.
MRI uses radio frequency pulses and magnetic field gradients applied to a subject in a strong homogenous magnetic field to produce viewable images. When a substance such as human tissue is subjected to a uniform magnetic field (polarizing field B0), the individual magnetic moments of the spins in the tissue attempt to align with this polarizing field, but precess about it in random order at their characteristic Larmor frequency. If the substance, or tissue, is subjected to a magnetic field (excitation field B1) which is in the x-y plane and which is near the Larmor frequency, the net aligned moment, or “longitudinal magnetization”, Mz may be rotated, or “tipped”, into the x-y plane to produce a net transverse magnetic moment Mt. A signal is emitted by the excited spins after the excitation signal B1 is terminated and this signal may be received and processed to form an image.
When utilizing these signals to produce images, magnetic field gradients (GxGy and Gz) are employed. Typically, the region to be imaged is scanned by a sequence of measurement cycles in which these gradients vary according to the particular localization method being used. The resulting set of received NMR signals are digitized and processed to reconstruct the image using one of many well known reconstruction techniques.
Current techniques for the acquisition of multi-slice fast spin echo (FSE) images require that each slice be imaged in separate breath-holds in order to attain black blood contrast in a gated sequence. Such conventional gated-FSE acquisitions are able to acquire images from only one spatial location per breath-held acquisition because the second inversion recovery RF pulse is slice selective only over the imaged slice.
It would therefore be desirable to have a technique to acquire black blood contrast images using fast spin echo acquisitions with improved multi-slice acquisition for efficient imaging that is capable of imaging across one or more R-R intervals.